Stress-buffer release lever and downhole plugging apparatus

ABSTRACT

The present invention discloses a stress-buffer release lever, which comprises an outer lever and an inner lever; the outer lever consists of a front end and a back end, wherein external threads are provided on both ends of the outer lever; a weakened section is set between the front end and the back end of outer lever; a co-axial through-hole is provided inside the outer lever, and internal threads are set on an inner surface of the through-hole; the inner lever&#39;s outer surface is provided with an external thread, the inner lever is set within the through-hole of the outer lever and is connected to the outer lever by the threads; the tensile strength of the inner lever is lower than that of the outer lever. The current invention also discloses a downhole plugging apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Chinesepatent application 201420105534.6, filed Mar. 10, 2014, the disclosureof which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a oil-gas production and a mineralmining field, particularly, to a downhole plugging apparatus andstress-buffer release lever which are used for downhole blocking.

2. General Background of the Invention

In the oil-gas production or mineral mining process, a wellbore mightneed to be blocked. Currently the most common way of the downholeblocking is by using apparatus for plugging. The existing downholeplugging apparatus is composed of an anchor component which is set on amandrel, a seal component and a release lever. After said existingplugging apparatus is put into a predetermined position in a well, itwill be fixed by squeezing the anchor component to have it anchored intoa casing wall. Meanwhile, the anchor component would squeeze the sealcomponent, and lead to its radial expansion so that the seal componentwould engage with a wellbore tubing to seal thereof.

The release lever is connected to an external claw by threads; the clawalso includes a clamping device that contacts with an upper anchor; theclamping device would compress the upper anchor and gets both the upperanchor and a lower anchor squeezing the seal component, so that it wouldconstrict in an axial direction and expand in an radial direction, thenthe seal component could be pressed against the casing wall tightly anda good sealing performance could be achieved. Finally, the anchorcomponent would anchor into the wall and the release lever will be cutwhen being pulled, and the existing downhole plugging apparatus will beleft in the well.

Because a connecting part of the release lever and the mandrel wouldbear a large stress during the setting process, the release lever needsto have a high tensile strength to ensure a reliable connection betweenthe release lever and the external claw as well as the mandrel, also toensure no deformation.

However, when it fractures, the release lever would bear very largestress which is close to its maximum strength, this will cause greattransient impact for the existing downhole plugging apparatus when therelease lever fractures, which impacts effective fixation of saiddownhole plugging apparatus.

BRIEF DESCRIPTION OF DRAWINGS

For a further understanding of the nature, objects and advantages of thepresent invention, reference should be had to detailed descriptionhereafter, read in conjunction with the following drawings:

FIG. 1 is a structural diagram of a stress-buffer release lever.

FIG. 2 is a structural diagram for a downhole plugging apparatus.

FIG. 3 is a state diagram of a downhole plugging apparatus in a settingstate.

FIG. 4 is a structural diagram of a upper anchor assembly.

FIG. 5 is a structural diagram of a lower anchor assembly.

FIG. 6 is a structural diagram of a upper lock nut.

FIG. 7 is a structural diagram of a lower lock nut.

FIG. 8 is a structural diagram of a stripper ring.

FIG. 9 is a structural schematic diagram of a slips.

FIG. 10 is a structural schematic diagram of a conical slip holder.

Wherein the names of related components are as below: 1—mandrel, 2—upperlock nut, 3—stripper ring, 4—slips, 5—conical slip holder, 6—middlerubber sleeve, 7—end rubber sleeve, 8—lower lock nut, 9—outer lever,10—inner lever, 11—wellbore wall—31—conical surface, 32—separateprotrusions, 51—conical surface, 52—separate protrusions, 81—conicalsurface, 82—separate protrusions, 91—front end, 92—back end, 93—weakenedsection, 94—through-hole.

DESCRIPTION OF THE INVENTION

One objective of the present invention is to provide a stress-bufferrelease lever having a high tensile strength as well as a enhancedanti-brittle fracturing feature, which would lower the stress when itbreaks and avoid a transient high intensity impact on a downholeplugging apparatus.

Yet another objective of the present invention is to provide thedownhole plugging apparatus which includes the stress-buffer releaselever.

Objectives of the present invention are realized as followed:

The stress-buffer release lever comprises an outer lever and an innerlever; the outer lever includes a front end and a back end, wherein boththe front end and the back end of the outer lever are threadedexternally, and a weakened section is provided between the front end andthe back end of the outer lever; a coaxial through-hole is providedinside the outer lever, wherein said through-hole's inner surface isthreaded; the inner lever's out surface is externally threaded, whereinthe inner lever is set within the through-hole of the outer lever and isconnected to the outer lever by threading; the tensile strength of innerlever is lower than that of the outer lever.

To ensure the stress-buffer release lever could connect with an externalclaw and a mandrel reliably without deformation during releasingprocess, said release lever needs to have a high tensile strength.However, its anti-brittle strength will decrease with the increase oftensile strength, thus a brittle fracture might occur when said releaselever breaks.

To solve this problem, an bi-layer structure of the outer lever and theinner lever is applied. The outer lever is of a high tensile strength soit can bear larger force without deformation, and a reliable connectionbetween the claw and the mandrel can be guaranteed; the inner lever isof a low tensile strength and it has strong anti-brittle ability. Whenpulling the release lever, the inner lever and the outer lever will workas a whole and greatly reduce the stress when the release lever breaks.Therefore, the transient high intensity impact on the downhole pluggingapparatus is avoided, which will effectively solve the problem that alooseness would possibly occur of the downhole plugging apparatus causedby transient high intensity impact when the release lever is departingfrom the mandrel.

Preferably, the weakened section is an annular groove on the outerlever. Preferably, a cross section of the said annular groove issemicircle-shaped, which can effectively avoid stress concentration.

Preferably, the cross-section of said annular groove is U-shaped.

Preferably, the outer lever is made of hard alloy steel; the inner leveris made of copper.

Another objective of the present invention is realized As followed:

The downhole plugging apparatus comprises the mandrel, a seal assemblyset on the mandrel, an upper anchor assembly and a lower anchor assemblywhich are connected to an upper end and a lower end of the mandrel,respectively, the stress-buffer release lever that is connected to thetop of mandrel by threading. The stress-buffer release lever includesthe outer lever and the inner lever; the outer lever consists of thefront end and the back end, both the front end and the back end of theouter lever are externally threaded, and the back end is connected withthe upper end of the mandrel by threading; the weakened section isprovided between the front end and the back end of the outer lever; thecoaxial through-hole is provided inside the outer lever, the interiorsurface of the through-hole is internally threaded; the outer surface ofthe inner lever is externally threaded, the inner lever is set in thethrough-hole of the outer lever and is connected to the outer lever bythreading; the tensile strength of inner lever is lower than that of theouter lever.

Preferably, the weakened section is the annular groove on the outerlever

Preferably, the cross-section of the annular groove is semicircle-shapedor U-shaped.

Preferably, the outer lever is made of hard alloy steel; and the innerlever is made of copper.

Further, the upper anchor assembly includes (a) a upper lock nut whichis connected to a thread at the top of the mandrel, (b) a stripper ringthat contacts the upper lock nut, (c) a plurality of slips that contactthe stripper ring, and (d) a conical slip holder that contacts theslips; the conical slip holder also contacts the seal assembly;

The lower anchor assembly includes (a) a lower lock nut which isconnected to a thread at the bottom of the mandrel, (b) a plurality ofslips that contact the lower lock nut and (c) a conical slip holder thatcontact the slips. The conical slip holder also contacts the said sealassembly.

To sum up, the present invention is advantaged as followed:

1. The stress-buffer release lever has the high external tensilestrength and the enhanced anti-brittle fracturing ability, which help toreduce the stress when it breaks, and the transient high intensityimpact on the downhole plugging apparatus can be avoided, thus it caneffectively prevent the downhole apparatus from being loosened bytransient high intensity impact when the release lever is departing fromthe mandrel.

2. The downhole plugging apparatus, comprising the stress buffer releaselever, can effectively solve the problem that looseness possibly causedby the transient high intensity impact when the release lever isdeparting from the mandrel.

To provide a better understanding for this utility, Embodiments will beillustrated hereafter:

Embodiment 1

As shown in FIG. 1, the stress-buffer release lever includes the outerlever 9 and the inner lever 10; the outer lever consists of the frontend 91 and the back end 92; the external threads are threaded on boththe front end 91 and the back end 92 of the outer lever 9; the weakenedsection 93 is set between the front end 91 and the back end 92 of theouter lever 9; the coaxial through-hole 94 is provided inside the outerlever 9, and the internal thread is threaded in the interior surface ofthe through-hole; the external thread is threaded on the outer surfaceof the inner lever 10; the inner lever 10 is arranged in thethrough-hole 94 of the outer lever 9 and is connected to the outer lever9 by threading; the tensile strength of inner lever 10 is lower thanthat of the outer lever 9.

The bi-layer structure, namely, the outer lever 9 and the inner lever 10is applied in the Embodiment; the outer lever 9 is made of the hightensile strength so it can bear larger stress without deformation, andthe reliable connection between the claw and the mandrel could beguaranteed; the inner lever 10 is made of the low tensile strength, andof the good anti-brittle ability. Since the inner lever 10 and outerlever 9 would work as a whole, when the fracture occurs, the breakingstress of the outer lever 9 would be reduced by the malleability of theinner lever 10, thus the fracture stress of the release lever will besignificantly reduced; therefore the transient high intensity impact onthe downhole plugging apparatus can be avoided.

Preferably, the outer lever 9 should be made of materials with the hightensile strength, like WQ890, WH100Q, WQ960, 45CrNiMoVA, 45 steel orhard alloy such as YG6 and YG8N etc can be used to manufacture an outerlever 9; and theoretically, the inner lever 10 is only required to bemade of materials with lower tensile strength than that of the outerlever 9 to reduce the stress when fracturing; however in practice, usingmaterials with good plasticity and anti-brittle fracture will workbetter, such as pure copper, pure aluminum, pure iron, low carbon steeland composite materials such as PTFE, etc.

Embodiment 2

As shown in FIG. 1, the weakened section 93 is the annular groove on theouter lever 9.

Embodiment 3

the cross-section of the annular groove is semicircle-shaped as shown inFIG. 3.

The semicircle-shaped cross-section of the annular groove caneffectively avoid stress concentration.

Embodiment 4

the cross-section of the annular groove is U-shaped as shown in FIG. 3.

The U-shaped cross-section of the annular groove can effectively preventstress concentration; moreover, it can reduce the width of the annulargroove and increase the depth of the annular groove, making it easier tocontrol a fracturing position of the annular stress-buffer releaselever.

Embodiment 5

As shown in FIGS. 1, 2 and 3, the downhole plugging apparatus comprises(a) the mandrel 1, (b) the seal assembly set on the mandrel 1, (c) theupper anchor assembly and (d) the lower anchor assembly connected to theupper and the lower end of the mandrel 1, respectively.

The downhole plugging apparatus also comprises (e) the stress-bufferrelease lever that is connected to the top of the mandrel by threading.The stress-buffer release lever includes the outer lever 9 and the innerlever 10; the outer lever consists of the front end 91 and the back end92; the external threads are threaded on both the front end 91 and theback end 92 of the outer lever 9; the weakened section 93 is set betweenthe front end 91 and the back end 92 of the outer lever 9; the coaxialthrough-hole 94 is provided inside the outer lever 9, and the internalthread is threaded in the interior surface of the through-hole; theexternal thread is threaded on the outer surface of the inner lever 10;the inner lever 10 is arranged in the through-hole 94 of the outer lever9 and is connected to the outer lever 9 by threading; the tensilestrength of inner lever 10 is lower than that of the outer lever 9.

As shown in FIG. 3, the front end 91 of the outer lever 9 is connectedto an external claw by threading; the claw includes the clamping devicewhich contacts the upper anchor assembly; when the clamping device exerta force on the upper anchor assembly, and the upper anchor assemblytogether with the lower anchor assembly would squeeze the seal assembly,leading to an axial constriction as well as a radial expansion of theseal assembly; this would force the upper anchor assembly and the loweranchor assembly anchoring into a wellbore wall 11 to accomplish fixingof the downhole plugging apparatus and the sealing of seal assembly,then the stress-buffer release lever will be pulled to break and thedownhole plugging apparatus will be left in the well.

When it breaks, the fracture stress on the stress-buffer release leveris relatively small, so is the transient impact strength for thedownhole plugging apparatus, thus it will not influence the connectionbetween the wellbore wall 11 and the upper anchor assembly or the loweranchor assembly, and the downhole plugging apparatus can be fixed morefirmly in the wellbore wall 11.

In the current Embodiment, the stress-buffer release lever could be anyof that described in embodiments 1˜4.

Embodiment 6

The current Embodiment provides a further illustration for the downholeplugging apparatus.

As shown in FIG. 2 and FIG. 4, the upper anchor assembly includes (a)the upper lock nut 2 which is connected to the threads 101 at the top ofthe mandrel 1, (b) the stripper ring 3 that contacts the upper lock nut2, (c) the plurality of the slips 4 that contact the stripper ring 3 and(d) the conical slip holder 5 that contacts the slips 4. The conicalslip holder 5 also contacts the said seal assembly.

As shown in FIG. 6, there is a threaded hole inside the upper lock nut 2so that the upper lock nut 2 could be connected with the mandrel 1 bythread 101.

As shown in FIG. 8, the mandrel 1 is sleeved by the stripper ring 3,which could move axially along the mandrel 1; an end face of thestripper ring 3 that contacts the upper lock nut 2 is plane; an oppositeend face of the stripper ring 3 is a conical surface 31 on which atleast one separate protrusions 32 are arranged evenly. As shown in FIG.9, each of the slips 4 contacts the conical surface 31 and is setbetween two adjacent separate protrusions 32.

As shown in FIG. 10, the mandrel 1 is sleeved by the conical slip holder5, which could travel axially along the mandrel 1 when bearing force;the end face of the conical slip holder 5 facing the stripper ring 3 isa conical surface 51 on which the separated protrusions 52 are arranged;the opposite end face of each of the slips 4 is in contact with theconical surface 51 and is between two adjacent separate protrusions 52;the opposite end face of conical slip holder is flat and it contactswith the seal assembly.

As shown in FIG. 2 and FIG. 5, the lower anchor assembly includes (a)the lower lock nut 8 which is connected to the threads 101 at the bottomof the mandrel 1, (b) the plurality of the slips 4 that contacts thelower lock nut 8, and (c) the conical slip holder 5 that contact theslips 4. The conical slip holder 5 also contacts the said seal assembly.

As shown in FIG. 7, there is a threaded hole inside the lower lock nut 8so that the lower lock nut 8 could be connected with the mandrel 1 bythread 101; the end face of the lower lock nut 8 contacting with theseal assembly is the conical surface 81 on which the separateprotrusions 82 are arranged; as shown in FIG. 10, one end of each of theslips 4 is contacted with the conical surface 81 and is set between twoadjacent separate protrusions 82.

As shown in FIG. 10, the mandrel 1 is sleeved by the conical slip holder5, which could travel axially along the mandrel 1 when bearing force.The end face of the conical slip holder 5 facing with the stripper ring3 is the conical surface 51 on which the separate protrusions 52 arearranged; the opposite end of each of the slips 4 is in contact with theconical surface 51 and is between two adjacent separate protrusions 52;the opposite end face of conical slip holder is flat and it contactswith the seal assembly.

While operating, the mandrel is first fixed via the stress-bufferrelease lever, then force is applied on the stripper ring 3. Thestripper ring 3 and the lower lock nut 8 would push the slips 4traveling on the conical surface 51 of the conical slip holder 5. At thesame time, the force will be transmitted to the seal assembly throughthe conical slip holder 5, leading to the axial constriction as well asthe radial expansion of the seal assembly and the teeth of the slips 4would anchor into the wellbore wall 11, keeping the seal assembly in thestate of compression and to realize sealing.

The seal assembly consists of a middle rubber sleeve 6 that sleeves themandrel 1 and an end rubber sleeves 7 set at both ends of the middlerubber sleeve 6.

Although each of the embodiment have been described in great detail, itis to be understood that numerous modifications, variations andadaptations may be made to the particular embodiments of the inventiondescribed above without departing from the scope of the invention whichis defined in the claims:

What is claimed is:
 1. A stress-buffer release lever, comprising: anouter lever 9 and an inner lever 10, wherein the outer lever 9 consistsof a front end 91 and a back end 92, external threads are threaded onboth the front end 91 and the back end 92; a weakened section 93 isprovided between the front end 91 and the back end 92; a coaxialthrough-hole 94 is provided inside the outer lever 9, wherein aninterior surface of the through-hole is internally threaded; an externalthread is threaded on an outer surface of the inner lever 10, whereinthe inner lever 10 is arranged in the through-hole 94 of the outer lever9 and is connected to the outer lever 9 by threading; and, a tensilestrength of inner lever 10 is lower than that of the outer lever
 9. 2.According to claim 1, the stress-buffer release lever furthercomprising: the weakened section 93 is an annular groove on the outerlever
 9. 3. According to claim 2, the stress-buffer release leverfurther comprising: a cross-section of the annular groove issemicircle-shaped.
 4. According to claim 2, the stress-buffer releaselever further comprising: The cross section of the annular groove isU-shaped.
 5. According to claim 1, the stress-buffer release leverfurther comprising: the outer lever 9 is made of hard alloy steel, theinner lever 10 is made of copper.
 6. According to claim 2, thestress-buffer release lever further comprising: the outer lever 9 ismade of hard alloy steel, the inner lever 10 is made of copper. 7.According to claim 3, the stress-buffer release lever furthercomprising: the outer lever 9 is made of hard alloy steel, the innerlever 10 is made of copper.
 8. According to claim 4, the stress-bufferrelease lever further comprising: the outer lever 9 is made of hardalloy steel, the inner lever 10 is made of copper.
 9. A downholeplugging apparatus, comprising: (a) a mandrel 1; (b) a seal assembly seton the mandrel 1; (c) an upper anchor assembly and (d) a lower anchorassembly, both of which are connected to the upper and the lower end ofthe mandrel 1, respectively; (e) a stress-buffer release lever that isconnected to the top of mandrel 1 by threading; the stress-bufferrelease lever includes an outer lever 9 and an inner lever 10, Whereinthe outer lever consists of a front end 91 and a back end 92, externalthreads are threaded on both ends, and the back end 92 is connected to aupper end of the mandrel 1 by threading, and, a weakened section 93 isset between the front end 91 and the back end 92 of outer lever 9; acoaxial through-hole 94 inside the outer lever 9, and internal threadwas provided on an inner surface of the coaxial through-hole 94, whereinan external thread is threaded on an outer surface of the inner lever10, and the inner lever 10 is arranged within the through-hole 94 of theouter lever 9 and is connected to the outer lever 9 by threading; and, atensile strength of inner lever 10 is lower than that of the outer lever9.
 10. According to claim 9, the downhole plugging apparatus furthercomprises: the weakened section 93 is an annular groove on the outerlever
 9. 11. According to claim 10, the downhole plugging apparatusfurther comprises: a cross-section of the annular groove issemicircle-shaped or U-shaped.
 12. According to claim 9, the downholeplugging apparatus further comprises: the outer lever 9 is made of hardalloy steel; the said inner lever 10 is made of copper.
 13. According toclaim 10, the downhole plugging apparatus further comprises: the outerlever 9 is made of hard alloy steel; the said inner lever 10 is made ofcopper.
 14. According to claim 11, the downhole plugging apparatusfurther comprises: the outer lever 9 is made of hard alloy steel; thesaid inner lever 10 is made of copper.
 15. According to claim 9, thedownhole plugging apparatus further comprises: the upper anchor assemblycomprises (a) a upper lock nut 2 which is connected to threads 101 at anupper end of the mandrel 1, (b) a stripper ring 3 that contacts theupper lock nut 2, (c) a plurality of slips 4 that contact the stripperring 3 and (d) a conical slip holder 5 that contact the slips 4, and theconical slip holder 5 also contacts the seal assembly; the said loweranchor assembly comprises (a) a lower lock nut 8 which is connected tothe threads 101 at a lower end of the mandrel 1, (b) the plurality ofthe slips that contact the lower lock nut 8, (c) the conical slip holder5 that contact the slips 4, and the conical slip holder 5 also contactsthe seal assembly.
 16. According to claim 10, the downhole pluggingapparatus further comprises: the upper anchor assembly comprises (a) aupper lock nut 2 which is connected to threads 101 at an upper end ofthe mandrel 1, (b) a stripper ring 3 that contacts the upper lock nut 2,(c) a plurality of slips 4 that contact the stripper ring 3 and (d) aconical slip holder 5 that contact the slips 4, and the conical slipholder 5 also contacts the seal assembly; the said lower anchor assemblycomprises (a) a lower lock nut 8 which is connected to the threads 101at a lower end of the mandrel 1, (b) the plurality of the slips thatcontact the lower lock nut 8, (c) the conical slip holder 5 that contactthe slips 4, and the conical slip holder 5 also contacts the sealassembly.
 17. According to claim 11, the downhole plugging apparatusfurther comprises: the upper anchor assembly comprises (a) a upper locknut 2 which is connected to threads 101 at an upper end of the mandrel1, (b) a stripper ring 3 that contacts the upper lock nut 2, (c) aplurality of slips 4 that contact the stripper ring 3 and (d) a conicalslip holder 5 that contact the slips 4, and the conical slip holder 5also contacts the seal assembly; the said lower anchor assemblycomprises (a) a lower lock nut 8 which is connected to the threads 101at a lower end of the mandrel 1, (b) the plurality of the slips thatcontact the lower lock nut 8, (c) the conical slip holder 5 that contactthe slips 4, and the conical slip holder 5 also contacts the sealassembly.